The clamour for an immediate ceasefire in Gaza is growing in intensity even as Israel's determination to press home its attack on Hamas grows more dogged. The unfolding result of this fatal divergence is both an escalating humanitarian disaster and a diplomatic debacle for the "international community" that tasked itself with bringing peace to Israel-Palestine.

The formidable capacity of Israel's leaders for ignoring international opinion is nothing new. But if they calculated, before launching the Gaza operation, that they would face only limited external opposition, they have been proven largely correct. The past few days have exposed just how little leverage foreign governments and organisations are able, or are willing, to bring to bear.

As always, the US wields the most clout. But as with Israel's ill-fated 2006 invasion of Lebanon, the Bush administration is sitting on its hands. US secretary of state Condoleezza Rice, whose endless shuttle diplomacy this year is now confirmed in its utter futility, did not even mention Israel's military assault in her first official statement on the situation.

Rice's exact words were: "The US strongly condemns the repeated rocket and mortar attacks against Israel and holds Hamas responsible for breaking the ceasefire and for the renewal of violence in Gaza. The ceasefire should be restored immediately. The US calls on all concerned to address the urgent humanitarian needs of the innocent people of Gaza."

Barack Obama's aides, in explaining the US president-elect's silence, are meanwhile sticking to their mantra that the US only has one president at a time. But as the carnage and the outrage mount, this hands-off stance begins to look less like tact and more like a sign of a man who, confronted by a raw conflict that has defeated many more experienced statesmen before him, lacks new ideas.

Obama and his replacement for Rice, Hillary Clinton, have closely followed the Bush line on the ostracism of Hamas as an illegitimate terrorist organisation. He condemned Hamas rocket attacks in emotive, personalised terms during a visit to Sderot in southern Israel earlier this year.

"If somebody was sending rockets into my house where my two daughters sleep at night, I'm going to do everything in my power to stop that. And I would expect Israelis to do the same thing," Obama said. Arab critics suggested at the time that a balancing line or two about the impact of the Israeli army on Palestinian family life in besieged Gaza would have been welcome.

All the same, some Israeli officials suspect Obama may prove more sympathetic to the Palestinians' overall predicament than his predecessor. That's given as a reason for them to act now in Gaza, while the more pliable George Bush is still notionally at the helm.

The initial response to the crisis from European countries, including Britain, has been mostly formulaic, comprising routine expressions of dismay at the loss of civilian life, harsh words for Hamas, and a gentle tap on Israel's shoulder. British prime minister Gordon Brown's words typified this tiptoeing.

Brown said: "I understand the Israeli government's sense of obligation to its population. Israel needs to meet its humanitarian obligations, act in a way to further the long-term vision of a two-state solution, and do everything in its power to avoid civilian casualties."

Brown added that "Gazan militants" should stop their rocket attacks immediately. But he did not specifically call on Israel to halt military operations. That bias was corrected today by foreign secretary David Miliband. He has been pushing hard in recent months to revive a plan for a comprehensive peace agreement between Israel and all its Arab foes. Miliband demanded both sides should now stop fighting to prevent further "unacceptable" loss of life.

Although Ban Ki-moon, the UN secretary-general, criticised what he called Israel's "excessive use of force", the UN security council was, as usual in the case of Israel-Palestine, too divided to agree on anything but a bland expression of concern. The responses of Arab governments, the Arab League, and Organisation of the Islamic Conference have also been generally strong on words but weak on action.

This familiar lack of courage reflects multiple, long-standing divisions between pro-western and non-aligned Arab governments, between supporters of the rival Fatah and Hamas factions, and more broadly between the alienated "Arab street" and the region's mostly unelected, mostly unloved leaders.

But whatever its origins, the practical effect of this collective impotence, coupled with the US and Europe's mealy mouthed approach, is to give Israel a free hand for almost as long as it wants.

The other main consequence is even more disturbing. To the people most affected by the violence, and to Arabs more generally, international inaction looks like complicity with Israel. It looks like collaboration.

All peace talks, bilateral or otherwise, are now on indefinite hold. And the longer the killing continues unchecked, the more radicalising and polarising its impact on ordinary people. It has been a dreadful few days in Gaza. But Iran's Revolutionary Guards and others of their militantly confrontational ilk in Syria and Lebanon must be loving every minute of it.